Electrocatalytic N=N coupling reaction mechanism on the Ni-based catalysts: A density functional theoretical study

Although electrocatalytic synthesis represents a promising frontier in energetic materials (EMs) development, the mechanistic understanding of the underlying catalytic processes remains elusive, posing both challenges and opportunities to optimize reaction pathways and enhance material performance. This study employs density functional theory (DFT) to investigate the reaction mechanism of the electrochemical oxidative coupling of 5-amino-1H-tetrazole (5AT) to produce 5,5'-azo-tetrazole (ZT), catalyzed by nickel (Ni) and nickel oxide (NiO) under alkaline conditions. Our findings reveal that the dehydrogenation reaction of 5AT follows the proton-coupled electron transfer (PCET) mechanism and involves two different pathways: direct dehydrogenation and dehydrogenation initiated by OH*. Crucially, the involvement of OH* shifts the dehydrogenation reaction on both Ni and NiO from endothermic to exothermic, thereby significantly enhancing reaction activity. In addition, OH* participation markedly suppresses the competitive oxygen evolution reaction (OER) on Ni and NiO surfaces, ensuring high selectivity towards ZT synthesis. The experimental results corroborate with DFT calculations, confirming that NiO is a more excellent catalyst than Ni, and underscoring the pivotal role of OH* in the 5AT oxidative coupling reaction. This work provides a theoretical foundation for the development of green and efficient synthesis of energetic azo compounds. The mechanism of electrocatalytic oxidation coupling of 5-amino-1 H -tetrazole on the Ni-based catalysts to synthesize 5,5'-azotetrazole was investigated. Density functional theory calculations and experimental validation indicate that OH* is the key species, converting the dehydrogenation step into a spontaneous process and enhancing reaction activity and selectivity. Comparisons of various descriptors reveal that NiO exhibits superior catalytic performance to Ni, providing theoretical support for the electrochemical synthesis of energetic materials. • DFT calculations elucidate the electrooxidative dehydrogenation of 5AT follows the Proton-Coupled Electron Transfer. • The adsorbed OH* in 5ATOR shifts the dehydrogenation reaction from endothermic to exothermic. • The experiment verifies the better electro-catalytic effect of NiO on 5ATOR.